“How could I apply this information?”
Although survival rates for premature infants have improved, long-term outcomes remain a concern, with a 5% to 10% prevalence of cerebral palsy and up to 40% prevalence of milder motor deficits.1–3 Can we identify infants born preterm at risk for long-term motor impairments to target for early intervention, or, ease caregiver and physician concerns when motor risk is low? Perinatal risk factors associated with poorer neurodevelopmental outcomes include intraventricular hemmorhage,4 periventricular leukomalacia,5 history of sepsis,6 extremely low birth weight, and low gestational age at birth.7 Neonatal and infant motor tests, such as the Test of Infant Motor Performance8 and the Alberta Infant Motor Scale,9 can help with early identification of motor impairments. However, even when medical risk factors and early motor assessments are considered together, our ability to develop a prognosis for longer-term motor outcomes remains quite limited.
Magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) may, one day, expand the existing information we have available to guide clinical decision-making around prognosis for infants born prematurely. In this study, premature infants with Bayley Scales of Infant Development, Third Edition, motor scores at least 1.5 standard deviations from the mean at 6 months corrected age had significantly lower subcortical gray matter volume at hospital discharge, compared to those with normal motor scores. Although this finding suggests a potential relationship between low volumes and motor outcomes, we must exercise caution with clinical application.
“What should I be mindful about in applying this information?”
Research exploring relationships between brain structure/function and motor outcomes will be important for physical therapists to review and incorporate into evidence-based practice. Several methodological limitations of the study highlight the challenges of this kind of research:
- Volumetrics included a small sample of relatively robust premature infants; only one-third had motor scores at or below 1.5 standard deviation at 6 months corrected age. Replication with a larger, more representative sample will be important.
- Regional volumes were measured manually which, although an accepted method, can introduce substantial measurement error. Blinded assessment by experienced technicians and inter/intra-rater reliability are essential.
- Subcortical grey matter volumes also included white matter which, given the relationship between white matter disease and prematurity, presents confounds.
When interpreting MRI/MRS studies, physical therapists must be ever mindful of the important difference between correlation and causation. If an association between brain structure/function and motor performance is identified, a causal link does not necessarily follow. Long-term follow-up studies are needed to substantiate that associations persist and are clinically relevant.
In short, “stay tuned” for future reports linking MRI/MRS with motor outcomes in premature infants, but “hold” on direct clinical application at this early stage.
Elise Towusewi, PT, DPT, PhD, PCS
MGH Institute of Health Professions and Massachusetts General Hospital, Boston, Massachusetts
Sheila Pallotta, PT, DPT, PCS
Massachusetts General Hospital, Boston, Massachusetts
1. Holsti L, Grunau RV, Whitfield MF. Developmental coordination disorder in extremely low birth weight children at nine years. J Dev Beliav Pediad. 2002;23:9–15.
2. Wilson-Costello D, Friedman H, Minich, et al. Improved neuromotordevelopmental outcomes for extremely low birth weighi infants in 2000–2002. Pediatrics. 2007;119:37–45.
3. Smith GC, Gutovich J, Smyser C, et al. Neonatal intensive care unit stress is associated with brain development in preterm infants [published online ahead of print October 4, 2011]. Ann Neurol, doi: 10.1002/ana.22545
4. Brouwer A, Groenendaal D, van Haaster 1-L, et al. Neurodevelopmenlal outcome of preterm infants with severe intraventricular hemorrhage and therapy for post-hemorrhagic ventricular dilation. J Pcdialr. 2008;152:648–654.
5. Nanba Y, Matsuji K, Aida N, et al. Magnetic resonance imaging regional 11 abnormalities at term accurately predict motor outcomes in preterm infants. Pediatrics. 2007;120:el0–el9.
6. Stoll Bj, Hansen Ni, Adams Chapman 1, et al. N e n rode vel op mental and growth impairment among extremely low-birth-weight infants with neonatal infection. JAMA. 2004;292:2357–2365.
7. Kleehl-Kohlendorfer L, Raiser E, Pupp Peglow U, et al. Adverse neurodevelopmental outcome in preterm infants: risk factor pro Hies for difference gestational ages. Acta Pcdiatr. 2009;98:792–796.
8. Campbell SK, Kolobe THA, Osten ET, et al. Evidence for the construct validity of the test of infant motor performance. Phys Ther. 1995:75:585–596.
9. Prins SA, von Lindern JS, van Dijk S, Versteegh FG. Motor development of premature infants born between 32 and 34 weeks [published online ahead of print September 7, 2011]. Int J Pcdiatr. doi: 10.1155/2010/462048